Use Symfony's ExpressionLanguage component for filters

[ogizanagi]

Fixes #99. A bit more verbose, but waaay more powerful and extensible.

  See https://symfony.com/doc/current/components/expression_language/syntax.html
  The current item is referred using "data", "d" or "_":

      php bin/console debug:stenope:content "App\Model\Author" --filter=data.active
      php bin/console debug:stenope:content "App\Model\Author" --filter=d.active
      php bin/console debug:stenope:content "App\Model\Author" --filter=_.active

  Negation:

      php bin/console debug:stenope:content "App\Model\Author" --filter='not d.active'
      php bin/console debug:stenope:content "App\Model\Author" --filter='!d.active'

  Contains:

      php bin/console debug:stenope:content "App\Model\Article" --filter='contains(_.slug, "symfony")'

  You can also use multiple filters at once:

      php bin/console debug:stenope:content "App\Model\Article" \
          --filter='not _.outdated' \
          --filter='contains(_.slug, "dev")' \
          --filter='"symfony" in _.tags' \
          --filter='_.date > date("2021-01-23")'

  Built-in functions are:

  * date
  * datetime
  * upper
  * lower
  * contains
  * starts_with
  * ends_with

Expressions can be used to filter using the ContentManager::getContents and in Twig as well.
New functions can be added using the stenope.expression_language_provider tag.

---

TODO

• Fix & add more tests

[Tom32i]

Very nice feature!

[Tom32i]

Hidden feature 👀

[ogizanagi]

Not really, it's documented already 😄 https://stenopephp.github.io/Stenope/supported-formats/#admonitions